> But overclocking is not the problem for udelay, it would err to the safe > side. The problem would be a BUS having < 8 MHz, and since the days of > 80286, they are hard to find. IMO having an option to set the bus speed> for those systems should be enough.

If you get it wrong you risk data corruption. Not good, not clever, notappropriate. Basically the use of port 0x80 is the right thing to do forISA devices and as 15 odd years of use has shown works reliably andsolidly for ISA systems.